POPULATION SUPPRESSION AND STERILITY RATES INDUCED BY VARIABLE SEX-RATIO, STERILE INSECT RELEASES OF CERATITIS-CAPITATA (DIPTERA, TEPHRITIDAE) IN HAWAII

Sterile insect releases of a pupal color-based genetic sexing strain o f the Mediterranean fruitfly, Ceratitis capitata (Wiedemann), were mad e during the summer and fall of 1991 in coffee plantations in Kauai, H I. Four treatments compared with respect to trap recapture and sterili ty rates induced in native populations were: (1) genetic sexing strain (almost-equal-to 99% males = males only), (2) genetic sexing strain ( males and females), (3) genetic sexing strain (high % female female), and (4) standard strain (males and females). Each week either 2 liters (almost-equal-to 120,000) of irradiated pupae for the bisexual popula tions or 1 liter of irradiated pupae for the unisexual populations wer e dye-marked and ground released in buckets. Adult flies emerged and d ispersed throughout individual (almost-equal-to 1 ha) coffee fields. F lies were trapped weekly in standard dry traps or in liquid protein tr aps. Coffee berry samples were collected weekly to determine egg steri lity rates, and females trapped in liquid protein were dissected for p resence of sperm and sperm type. A new technique was developed to type sperm as either sterile (irradiated) or wild in mated females. An est imate of sterile fly competitiveness based on relative degrees of egg hatch suppression indicated an overall three- to five-fold increase in competitiveness of the males-only strain compared with the standard b isexual strain. Significantly, however, this difference even widened t o a qualitative degree by the end of the test.